CNT Buckypaper Roll-to-Roll Deposition for Thick Films
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Solution Overview
Problem
Existing methods for producing carbon nanotube (CNT) buckypapers face challenges in scaling up to produce thick, meter-long films efficiently, due to issues with solubility, processing difficulties, and the need for surfactants or binders.
Innovation Solution
A roll-to-roll compatible deposition technique is used to produce large area, meter-long thick films of CNT buckypaper by preparing a dissolved CNT salt solution, depositing it onto a porous filter, and then drying and delaminating the buckypaper to form a freestanding film without the need for surfactants or binders.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If traditional filtration method is used to produce CNT buckypaper, then the buckypaper can be obtained, but the production process is extremely challenging and time-consuming when scaling up to produce thick, meter-long films
Solution Approach 1:
The patent changes the physical and chemical parameters of the CNT material by functionalizing the CNT surfaces and forming CNT salts, which fundamentally alters the solubility and processability characteristics. This enables the material to be processed in solution form through roll-to-roll deposition, achieving meter-long thick films with high productivity that were previously impossible with traditional filtration methods
Solution Approach 2:
The patent replaces the mechanical filtration process with a chemical solution-based deposition process. Instead of filtering CNT suspensions through membranes (mechanical separation), the invention uses roll-to-roll deposition of CNT salt solutions followed by controlled oxidation to form the final buckypaper, dramatically simplifying the manufacturing process and enabling continuous production of long films
2Quantity of substance
If CNTs are processed in film form using traditional methods, then films can be produced, but the poor solubility of CNTs results in low concentrated dispersions requiring large volumes of solution
Solution Approach 1:
The patent fundamentally changes the solubility parameter of CNTs by converting them into soluble salt forms through chemical functionalization. The CNT salts can be dissolved in polar aprotic solvents to achieve high concentrations (up to 5 mg/mL), eliminating the need for large volumes of dilute suspensions required by traditional methods
3Volume of moving object
If thick films of CNT buckypaper are deposited using spray-coating, then film thickness can be increased, but the low CNT content in solution makes the deposition process very slow
Solution Approach 1:
The patent changes the concentration parameter of the CNT solution by using soluble CNT salt formulations that can achieve high CNT concentrations (up to 5 mg/mL). This allows thick films to be deposited rapidly through roll-to-roll methods, achieving both the desired film thickness and high deposition speed, unlike spray-coating which is limited by low CNT content in traditional suspensions
4Ease of manufacture
If surfactants or binders are added to process CNTs, then the processing difficulty is reduced, but the purity and performance of the final buckypaper deteriorates
Solution Approach 1:
The patent uses CNT salts as an intermediary form that enables processing without requiring traditional surfactants or binders. The salt formulation acts as a temporary processing aid that can be completely removed through oxidation and washing steps, leaving pure CNT buckypaper with superior performance. This intermediary approach solves the contradiction by enabling easy processing while maintaining final product purity
Solution Approach 2:
The patent employs a process where the CNT salt formulation and associated processing chemicals are completely discarded through oxidation and washing steps. The temporary salts and surfactants used during processing are removed to recover pure CNT buckypaper, ensuring high purity and performance in the final product while still benefiting from the ease of processing provided by the salt formulation during manufacturing
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This method allows for the production of thick, stable CNT films with low sheet resistance, high electrical conductivity, and excellent mechanical stability, enabling their use in thermoelectric modules and battery electrodes with improved performance and longevity.
Implementation Method 1
preparing a dissolved CNT salt using a procedure comprising the following step: i) providing a stock solution of reductive alkali metal, preferably the alkali metal is selected from potassium or sodium, naphthalenide (Np) in a polar aprotic solvent
Implementation Method 2
depositing the solution obtained in a) via roll-to-roll compatible deposition method onto a porous filter used as temporary substrate, preferably the temporary substrates are porous PTFE filter sheets, in presence of an oxidizing atmosphere at a pressure of between 0,8 and 1,5 bar
Implementation Method 3
removing the solvent and partially drying the wet buckypaper obtained in b) by applying a rough vacuum across the porous filter substrate
Data Source
Figure 1(a)~1(c)
Figure 2
Figure 3
AI summary
The invention relates to a new method for preparing more than micron thick and meter-long carbon nanotube (CNT) buckypapers and more particularly using a roll-to-roll compatible fabrication approach. In addition, the buckypaper is obtained for the fabrication of the n- and p-type components of the thermoelectric module, as well as for electrode components in chemical storage devices through a post-deposition process involving partial oxidation of the CNTs and neutralization of the dopant.